Current practice for alcohol measurements is based upon either blood measurements or breath testing. Blood measurements define the gold standard for determining alcohol intoxication levels. However, blood measurements require either a venous or capillary sample and involve significant handling precautions in order to minimize health risks. Once extracted, the blood sample must be properly labeled and transported to a clinical laboratory or other suitable location where a clinical gas chromatograph is typically used to measure the blood alcohol level. Due to the invasiveness of the procedure and the amount of sample handling involved, blood alcohol measurements are usually limited to critical situations such as for traffic accidents, violations where the suspect requests this type of test, and accidents where injuries are involved.
Because it is less invasive, breath testing is more commonly encountered in the field. In breath testing, the subject must expel air into the instrument for a sufficient time and volume to achieve a stable breath flow that originates from the alveoli deep within the lungs. The device then measures the alcohol content in the air, which is related to blood alcohol through a breath-blood partition coefficient. The blood-breath partition coefficient used in the United States is 2100 (implied units of mg EtOH/dL blood per mg EtOH/dL air) and varies between 1900 and 2400 in other nations. The variability in the partition coefficient is due to the fact that it is highly subject dependent. In other words, each subject will have a partition coefficient in the 1900 to 2400 range that depends on his or her physiology. Since knowledge of each subject's partition coefficient is unavailable in field applications, each nation assumes a single partition coefficient value that is globally applied to all measurements. In the U.S., defendants in DUI cases often use the globally applied partition coefficient as an argument to impede prosecution.
Breath measurements have additional limitations. First, the presence of “mouth alcohol” can falsely elevate the breath alcohol measurement. This necessitates a 15-minute waiting period prior to making a measurement in order to ensure that no mouth alcohol is present. For a similar reason, a 15 minute delay is required for individuals who are observed to burp or vomit. A delay of 10 minutes or more is often required between breath measurements to allow the instrument to return to equilibrium with the ambient air and zero alcohol levels. In addition, the accuracy of breath alcohol measurements is sensitive to numerous physiological and environmental factors.
Multiple government agencies, and society in general, seek non-invasive alternatives to blood and breath alcohol measurements. Quantitative spectroscopy offers the potential for a completely non-invasive alcohol measurement that is not sensitive to the limitations of the current measurement methodologies. While non-invasive determination of biological attributes by quantitative spectroscopy has been found to be highly desirable, it has been very difficult to accomplish. Attributes of interest include, as examples, analyte presence, analyte concentration (e.g., alcohol concentration), direction of change of an analyte concentration, rate of change of an analyte concentration, disease presence (e.g., alcoholism), disease state, and combinations and subsets thereof. Non-invasive measurements via quantitative spectroscopy are desirable because they are painless, do not require a fluid draw from the body, carry little risk of contamination or infection, do not generate any hazardous waste, and can have short measurement times.
Several approaches have been proposed for the non-invasive determination of attributes of biological tissue. These systems have included technologies incorporating polarimetry, mid-infrared spectroscopy, Raman spectroscopy, Kromoscopy, fluorescence spectroscopy, nuclear magnetic resonance spectroscopy, radio-frequency spectroscopy, ultrasound, transdermal measurements, photo-acoustic spectroscopy, and near-infrared spectroscopy. However, these systems have not replaced existing approaches for the measurement of alcohol concentration.
US Patent application 20050090750 (Ediger) discloses the use of Raman spectroscopy of tissue to screen for diabetes. It does not disclose the use of Raman spectroscopy for the measurement of alcohol concentration or application as a biometric method.
U.S. Pat. No. 5,553,616 (Ham) discloses instruments and methods for noninvasive tissue glucose level monitoring via Raman spectroscopy and spectral processing by neural networks and fuzzy logic. Ham does not describe measurement of any other tissue property such as alcohol, or any method of screening for alcohol, or determining biometric identity.
U.S. Pat. No. 5,582,168 (Samuels) discloses apparatus and methods for measuring characteristics of biological tissues and similar materials. These apparatus and methods are described with respect to measurements of the human eye. In addition, the correction methodologies described by these inventors involve only measurements of the elastically scattered excitation light. Samuels describes a simple linear correction technique. Samuels does not disclose noninvasive measurements that allow determination of alcohol concentration or biometric measurements.
U.S. Pat. No. 5,882,301 (Yoshida) discloses methods and apparatus for obtaining Raman emission from intraocular substances including advanced glycated endproducts (AGEs). Yoshida does not disclose noninvasive measurements that allow determination of alcohol concentration or biometric measurements.
U.S. Pat. No. 6,044,285 (Chaiken) discloses a system based upon Raman spectroscopy for measuring blood glucose. The described technique relies upon an absorbing species such as hemoglobin acting as a temperature probe. Chaiken does not disclose noninvasive measurements that allow determination of alcohol concentration or biometric measurements. In addition, Chaiken does not describe methods for correction techniques to compensate for local skin absorption or scattering.
U.S. Pat. No. 6,167,290 (Yang) discloses a Raman spectroscopy system for noninvasively measuring blood glucose. Yang does not disclose noninvasive measurements that allow determination of alcohol concentration or biometric measurements. Furthermore, Yang does not describe methods for correction techniques to compensate for local skin absorption or scattering in order to recover the intrinsic Raman emission signal.
U.S. Pat. No. 6,289,230 (Chaiken) describes an apparatus for the non-invasive quantification of glucose via Raman spectroscopy. Chaiken does not disclose noninvasive measurements that allow determination of alcohol concentration or biometric measurements. In addition, Chaiken does not describe methods for correction techniques to compensate for local skin absorption or scattering.
U.S. Pat. No. 6,352,502 (Chaiken) describes an apparatus based upon Raman spectroscopy for the noninvasive characterization of skin and detection of skin abnormalities. Chaiken does not disclose noninvasive measurements that allow determination of alcohol concentration or biometric measurements. Chaiken does not describe methods to extract the intrinsic Raman emission from the detected signal nor multivariate techniques to quantitatively predict analyte concentration.
U.S. Pat. Nos. 6,181,957 and 6,424,850 (Lambert) describe a noninvasive glucose monitor that uses Raman spectroscopy. The inventions require interrogation of the anterior chamber of the eye. Furthermore, other than Fluorescence subtraction, Lambert does not disclose algorithms or methods for recovering intrinsic Raman emission or other techniques to compensate for local tissue variations.
U.S. Pat. No. 6,560,478 (Alfano) describes an apparatus based upon Raman spectroscopy for examining biological materials. Alfano discloses that the technique can be applied for the diagnosis of disease by measuring characteristic Raman emission associated with blood glucose and other constituents. Alfano does not disclose noninvasive measurements that allow determination of alcohol concentration or biometric measurements. Also, Alfano does not disclose algorithms or methods for recovering intrinsic Raman emission or other techniques to compensate for local tissue variations.
U.S. Pat. No. 7,257,987 and applications 20070271997 and 20060144126 (O'Brien) disclose apparatuses for measuring analytes in gases including alcohol in breath. The present invention involves in vivo, rather than ex vivo, alcohol measurements and therefore does not involve the use of breath. Furthermore, none of the O'Brien patents or applications disclose algorithms or methods for recovering intrinsic Raman emission or other techniques to compensate for local tissue variations.
US Patent application 20070239992 (White) discloses the use of spectroscopic alcohol measurements as part of an automotive interlock. White does not disclose any embodiments of Raman systems for alcohol measurements nor does White disclose algorithms or methods for recovering intrinsic Raman emission or other techniques to compensate for local tissue variations.
U.S. Pat. No. 6,070,093 (Oosta) discloses the use of multiplex sensors that combine multiple measurement modalities (e.g. absorbance combined with Raman) to measure analytes. The present invention does not require the combination of multiple modalities. Furthermore, Oosta does not disclose embodiments of suitable Raman systems for alcohol measurements nor does Oosta disclose algorithms or methods for recovering intrinsic Raman emission or other techniques to compensate for local tissue variations.
A research group at Duke University (Brady) has disclosed embodiments of multimodal multiplex Raman spectroscopy for measuring alcohol. Multimodal Multiplex Raman uses multiple excitation lasers within a single instrument, each having a different lasing wavelength. Raman spectra are then collected from a sample using each laser. Additional details can be found in “Multimodal multiplex Raman spectroscopy optimized for in vivo chemometrics”, Biomedical Vibrational Spectroscopy III: Advances in Research and Industry, Proc. of SPIE Vol. 6093 (2006). The present invention does not require the use of multiple excitation lasers.
Instruments and methods useful in Raman spectroscopy like that in the present invention have been described for other applications. See, e.g., Toshima et al., Jpn J Opthalmol, 1990; Nie et al., Exp Eye Res, 1990 (evaluation of lens water content, and cataract progression); Sebag et al., Invest Opthalmol Visual Sci, 1994 (evaluation of the progression of retinopathy); Shim and Wilson, J Raman Spectroscopy, 1996 (characterization of fundamental Raman-active bonds in skin); Caspers et al., Biospectoscopy, 1998 and Caspers et al., J Invest Derm, 2001, (study of natural moisturizing factor in stratum corneum); Caspers et al., Biophysical J, 2002 (Raman confocal microscopy of skin).